title: Crystal structure of a Na+-bound Na+,K+-ATPase preceding the E1P state.
abstract: Na(+),K(+)-ATPase pumps three Na(+) ions out of cells in exchange for two K(+) taken up from the extracellular medium per ATP molecule hydrolysed, thereby establishing Na(+) and K(+) gradients across the membrane in all animal cells. These ion gradients are used in many fundamental processes, notably excitation of nerve cells. Here we describe 2.8 Å-resolution crystal structures of this ATPase from pig kidney with bound Na(+), ADP and aluminium fluoride, a stable phosphate analogue, with and without oligomycin that promotes Na(+) occlusion. These crystal structures represent a transition state preceding the phosphorylated intermediate (E1P) in which three Na(+) ions are occluded. Details of the Na(+)-binding sites show how this ATPase functions as a Na(+)-specific pump, rejecting K(+) and Ca(2+), even though its affinity for Na(+) is low (millimolar dissociation constant). A mechanism for sequential, cooperative Na(+) binding can now be formulated in atomic detail.
authors.affiliation: Institute of Molecular and Cellular Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan.
authors.forename: Ryuta
authors.initials: R
authors.lastname: Kanai
authors.forename: Haruo
authors.initials: H
authors.lastname: Ogawa
authors.forename: Bente
authors.initials: B
authors.lastname: Vilsen
authors.forename: Flemming
authors.initials: F
authors.lastname: Cornelius
authors.forename: Chikashi
authors.initials: C
authors.lastname: Toyoshima
mesh_terms: D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D007668:Kidney / Q000201:enzymology; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D012964:Sodium / Q000737:chemistry*; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry*; D013552:Swine
chemical_list: D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase